Ultraviolet radiation from both sunlight and artificial sources has been divided into three bands (UVA, UVB, and UVC) which emit different quantities of energy
UVA radiation is present in the sunlight reaching the earth's surface and has a wavelength of 320 to 400 nanometers (nm.). UVA radiation can cause tanning of the skin but is weak in causing reddening of the skin.
UVB radiation is present in the sunlight reaching the earth's surface and has a wavelength of 290 of 320 nm. UVB causes the sunburn reaction which also stimulates pigmentation (tanning) in the skin.
Ultraviolet energy absorbed by the human skin can produce an erythemal reaction (redness of the skin caused by dilatation and congestion of the capillaries). The intensity of erythemal reaction is generally dependent upon the amount of energy absorbed.
The majority of malignant melanomas are caused by heavy sun exposure in white-skinned populations. Incidence rates of malignant melanomas are highest Australia/New Zealand, where it is the third most common cancer in both males and females. Also, incidence rates are increasing rapidly in many countries, including in the Nordic countries, where the increase has been attributed to excessive sun exposure during holidays at lower latitudes.
According to Cancer Research UK, in 2011 malignant melanoma was the 5th most common cancer in the UK, accounting for 4% of all new cases. In males and females separately, malignant melanoma was the 6th most common cancer (4% each of the male and female total). In 2011, this amounted to 13,348 new cases of malignant melanoma in the UK. In England and Wales there are about 2,000 deaths each from melanoma and in 2012 there were around 55,500 deaths from melanoma worldwide.
Also, malignant melanoma incidence has an unusual age related pattern when compared with most other cancers. In the UK between 2009 and 2011, an average of 27% of cases was diagnosed in those aged under 50 years.
Malignant melanoma incidence rates have increased overall in Great Britain since the mid-1970s. For males, incidence rates were almost seven times higher in 2009-2011 than in 1975-1977. For females, the increase is smaller but rates have still quadrupled between 1975-1977 and 2009-2011. Since the mid-1970s in Great Britain, malignant melanoma incidence rates have increased more rapidly than any of the current ten most common cancers in males and females.
Most of this increase is attributed to changes in sun-related behaviour such as an increase in frequency of holidays abroad over time. A study published in December 2011 estimated that around 86% of malignant melanomas in the UK in 2010 were linked to exposure to UVR from the sun and sunbeds.
However, some studies have shown that the use of sunscreen does not necessarily reduce the risk of malignant melanoma, because consumers reported that sunscreen use enabled them to spend more time sunbathing and/or because the subjects would still strive to achieve a sun tan, often because a tan is viewed by the consumer as being healthy.
Therefore, there is a need for a formulation that will allow a consumer to have the appearance of a healthy tan, whilst protecting the skin from the undesirable effects of ultraviolet light. Such a composition would comprise a UV filter and a sunless tanning system.
Attempts have been made to provide such a composition comprising a UV filter and DHA, which is considered the most effective sunless tanning system.
One disadvantage of the use of a sunless tanning system, such as DHA is that the appearance of a self-tan can confuse the user into many into thinking that they have a base tan and that they can then sit in the sun without getting burned. However, it is well understood that sunless tanners alone provide only a minimal amount of sun protection.
However, even if a sunless tanning system is combined with a UV filter, the sun-protective abilities generally do not last longer than a few hours, whereas the self-tan may last for as much as about 7-10 days.
It is known to combine a sunless tanning system with a UV filter, but the two interact and the effectiveness of the UV filter can be diminished. A sunless tanning system, such as DHA, provides its optimum effect at a pH of about 3 to 4. However, most UV filters comprise an organic ester, which has the potential to hydrolyse at low pH. Furthermore, DHA is incompatible with mineral UV filters, such as titanium dioxide.
US Patent application No. 2010/0303745 attempts to address the problem of the interaction of the UV filter and the sunless tanning system by using a UV filter with a high SPF. U.S. '745 describes a composition having a sunblock and tanning effect containing dihydroxyacetone and a broad spectrum UV filter having a high SPF of at least about 25.
European Patent application No. 2194958 describes the problem of the interaction of the UV filter and the sunless tanning system by the inclusion of a photostabiliser, such as, a copolymer of adipic acid and neopentyl glycol, to allow the sunscreen agent to remain photostable when subjected to said UV radiation and maintain a portion of the characteristic of UV radiation absorbance.
Therefore, there is a need for an improved formulation which provides UV protection for the skin, whilst providing the consumer with the appearance of a sunless tan. In particular, there is a need for a formulation that comprises a sunless tanning system component and a UV filter component, which prevents or hinders the interaction between the two components.